Method for charging submersible chambers



P 1959 E. L. NEWELL ET AL 2,902,803

METHOD FOR CHARGING SUBMERSIBLE CHAMBERS Original Filed Oct. 28, 1952 4Sheets-Sheet 1 FIGJ IN V EN TORS E. L. NEWELL H WELLS BY flaw M ATTORNEYSept. 8, 1959 E. 1. NEWELL ETAL 2,902,803

METHOD FOR CHARGING SUBMERSIBLE CHAMBERS Original Filed 00%. 28, 1952 4Sheets-Sheet 2 1 I7 v 25 l8- I f 24' w A Q7 1: 8 I e 5 i4 L: /AMPLIFIERFIG 5 INVENTORS E. L.NEWELL P. H. WELLS ATTORNEY Sept. 8, 1959 E. L.NEWELL ET AL 2,902,803

METHOD FOR CHARGING SUBMERSIBLE CHAMBERS Original Filed Oct. 28, 1952 4Sheets$heet 3 FIG.6

,AMPLIFIERV [Tn F165. 7 4

g INVENTORS E.L.NEWELL P. H.WELLS ATTDRN EX Sept. 8, 1959 E. L. NEWELLETAL 2,902,803

METHOD FOR CHARGING SUBMERSIBLE CHAMBERS Original Filed 001:. 28, 1952 4Sheets-Sheet 4 ATTORNEY;

United States Patent NIETHOD FOR CHARGING SUBMERSIBLE CHAMBERS Originalapplication October 28, 1952, Serial No. 317,278. Divided and thisapplication February 18, 1959, Serial No. 794,115

4 Claims. c1. 53-37 The present invention relates to submersiblechambers suitable for extended operation under relatively largehydrostatic pressures and more particularly to submersible chamberscontaining electronic apparatus and arranged to provide an internalpressure substantially equal to the external hydrostatic pressure.

This application is a divisional application of copending applicationSerial No. 317,278, filed October 28, '1952, by Earl L. Newell, PhilipH. Wells and Clifford H. Cramer.

As described in the copending patent application of H. F. Wilder, SerialNo. 229,146, filed May 31, 1951, now U.S. Patent No. 2,637,784, manyadvantages are secured by providing a repeating amplifier in a submergedportion of a submarine cable circuit. Since electronic apparatussuitable for use at the low frequencies normally employed in telegraphiccommunication over submarine cable circuits is inherently bulky, it isimpractical to provide a housing for a submerged repeating amplifierwhich will maintain atmospheric pressure at substantial depths. Moreparticularly, it would be very diflicult to provide a relatively largecontainer for unattended installation over a long period of time andwhich would maintain a high external-internal pressure differential. Forexample, atypical repeater installation might be at a depth at which ahydrostatic pressure of 750 pounds per square inch would be encountered.Accordingly, the housing should have an internal pressure substantiallyequal to the external hydrostatic pressure.

Since it is not possible to operate electrical apparatus in sea water,the repeater housing should be filled with an insulating fluid such asoil. Delicate electronic components, such as vacuum tubes, may beencased in small sealed containers located within the housing and beingdesigned to maintain substantially atmospheric internal pressures. Apressure equalizing mechanism must be provided to transmit to theinsulating fluid the increasing hydrostatic pressures encountered as therepeater is lowered. The equalizing mechanism must also provide areservoir to compensate for voids within the repeater housing resultingfrom incomplete filling thereof and for decreases in fluid volume withthe temperature drop.

Bellows arrangements have heretofore been used to equalize the internaland external pressures of a submerged casing. However, arrangementsheretofore employed have not been suitable for unattended use over longperiods of time in deep salt water. Corrosion and mechanical failure ofthe bellows tend to admit sea water into the interior of the casing.Moreover, a small amount of seepage over a long period of time willpermit enough water to enter the casing to seriously damage theequipment therein. Accordingly, it is an object of the invention toprovide an improved method of filling housing for a submersiblerepeater, the housing being arranged to provide an internal pressuresubstantially equal to the external hydrostatic pressure.

Still another object is to secure additional safety of ice 2 componentsand reliability of operation in submerged repeaters through increasingthe reserve volumetric capacity of expansible members, without increaseof size, weight, or complexity of those members.

A further object is to lengthen the average service life of submergedrepeaters by providing a more effective means of compensating for theoccasional leakage of liquid into the hermetically sealed containersused for housing certain components such as thermionic tubes andswitches operated at atmospheric pressure 'within the chamber.

Other objects and advantages of the invention will be apparent from thefollowing description.

In accordance with the invention, a submersible chamber containingelectronic apparatus and intended for use where subject to changes intemperature and hydrostatic pressure is filled with an electriciallyinsulating fluid, a bellows member being included within the chamber totransmit external pressure changes to the fluid within the chamber andto compensate for voids occurring within the chamber due to temperaturechanges of the insulating fluid, additional pressure translating meansbeing pro vided to transmit external pressure variations to' the bellowsmember and to prevent water from reaching the bellows member.

The invention will now be described in greater detail with reference tothe appended drawing in which:

Figs. 1, 2 and 3 are views of a submerged repeater housing embodying thepresent invention;

Figs. 4 and 5 illustrate one pressure equalizing arrangement for thehousing of Figs. 1 to 3, constructed in accordance with the invention;

Figs. 6 and 7 illustrate a second form of pressure equalizingarrangement constructed in accordance with the invention;

Fig. 8 is a schematic view of a submersible repeater housing and afilling mechanism therefor employing a vacuum pump;

Fig. 9 is a schematic view of an alternative arrange ment wherein apressure pump is shown for filling insulating fluid into the housing;and

Fig. 10 is a schematic diagram showing a further arrangement for fillingthe repeater housing with insulating fluid, employing a vacuum pump.

Referring now to the drawing and more particularly to Fig. 1, there isshown a front view of a submerged repeater housing H comprising a hollowtank member 10, a cable entrance chamber 11 and a supporting ring 12.The structural elements of housing H are preferably cornposed of steel.Tank member 10 is provided with an upper flange 13 fastened to a coverplate 14 by bolts such as 15 arranged along the outer edges of flange13. Flange 13 and cover plate 14 are separated by a gasket 8 made of amaterial such as synthetic rubber which resists salt water.

Cover plate 14 forms the bottom of cable entrance chamber 11. Chamber 11is also provided with a top plate 16 and side plates 17 and 18 shownsectioned. Not shown in Fig. 1 are back and front plates which, togetherwith side plates 17 and 18, serve to protect the cable entrance chamber.Supporting ring 12 is fastened to top plate 16 by means of a pair ofnuts 19.

Repeater housing H is supported by two lengths of steel rope 20 and 21.One end of each length is formed into an eye which is secured to ring 12by a link member. The other end of each length is spliced to the armorwires of respective cable sections 22 and 23 in such manner as toprovide slack in cable sections 22 and 23 between the splices and therepeater housing. Cable sections 22 and 23 enter the cable entrancechamber through entrance ports in side plates 17 and 18, respectively.The

about the entrance ports and are fastened to the armor wires outside theports, thereby providing a rigid mechanical coupling which will minimizestrain on the cable conductors.

' Cable section 23 is preferably a bicore cable so that a remote seaearth may be provided for the repeating amplifier input. The repeatingamplifier output ground is preferably effected on housing H. The twocable conductors from cable section 23 are passed into tank memberthrough water-tight cable entrance glands 24 and 24. In Fig. l, gland 24is hidden behind gland 24. The single cable conductor from cable section22 is passed into tank member 10 through a water-tight cable entrancegland 25.

In Fig. 2, which is a side view of the repeater housing, there is showntank member 10, ring 12, flange 13, cover plate 14, top plate 16, sideplate 17 and cable section 22. Also shown in Fig. 2 are front and backplates 26 and 27, respectively, which were not illustrated in Fig. 1. Noefiort is made to make cable entrance chamber 11 watertight, theenclosing plates being provided only to prevent mechanical injury to thecable conductors and their insulation. As is evident from Figs. 1 and 2,each of plates 17, 13, 26 and 27 is bolted to top plate 16 and to coverplate 14.

In Fig. 3, which is a sectional view of Fig. 1, taken along line 3-3,there can be seen cable entrance gland 24' which was hidden in Fig. 1.Also shown in Fig. 3 are four apertures 28 which permit entrance of seawater into a portion of tank member 10. As can be seen from Fig. 3, tankmember 10 and cable entrance chamber 11. have generally rectangularcross-sections.

Referring now to Fig. 4, the lower portion of cable entrance chamber 11and the upper portion of tank member 10 are shown in cross-section. Ahollow metal cylinder 30 having flanges at the upper and lower endsthereof is included within tank member 10. The upper flange of cylinder30 is fastened to cover plate 14 by bolts, a gasket 31 being provided toinsure proper sealing. Apertures 23 in cover plate 14 are arranged toadmit sea water into the upper end of cylinder 30. A piston 32 isincluded within cylinder 30 and is arranged to prevent admission of seawater to the lower portion of cylinder 30 and to transmit thehydrostatic pressure to an oil reservoir comprising the lower end ofcylinder 30 and a thin-walled cylindrical metallic bellows 33.

The lower flange of cylinder 30 is fastened to a plate 34 by bolts, agasket 35 being employed to insure an oiltight seal. A nipple 36 screwedinto an opening in plate 34 and into an opening in the top of bellows 33provides mechanical support for bellows 33 and serves as a channel forthe transfer of oil between the lower portion of cylinder 30 and bellows33.

As the repeater housing is lowered through water, the increasinghydrostatic pressure exerted on the top of piston 32 causes piston 32 totravel toward the bottom of cylinder 30, thereby applying asubstantially equal pressure to the oil in the reservoir.. Increasingpressure of oil in bellows 33 causes the walls thereof to diverge,thereby transmitting the pressure to oil within the remainder of tank10.

The lower portion of tank 10 contains the desired electronic apparatus,portions of which may be enclosed within small sealed chambers foroperation at normal surface pressures. A number of large electroniccomponents, and in particular transformers and oil-filled capacitors,can conveniently be operated in oil at high hydrostatic pressures, theoil providing excellent insulation. The three cable conductors referredto hereinbefore are passed through glands 24, 24' and and into the lowerportion of tank T for suitable connection to the electronic apparatus. Asuitable electronic circuit for use in the repeater is shown in thecopending patent application of P. H. Wells et al., Serial No. 229,193,filed May 31, 1951, now U. S. Patent No. 2,794,853. Additional ap- 4paratus for inclusion in tank member 10 is illustrated in the copendingpatent application of F. B. Bramhall et al., Serial No. 229,191 filedMay 31, 1951, now U.S. Patent No. 2,658,945.

Since the electronic apparatus will not completely fill the lowerportion of tank member 10, and since oil has a relatively high volmetrictemperature coeflicient of expansion solid, light-weight inert fillermaterial such as pieces of sheet aluminum cut to fit the space, whichhas a lower volumetric temperature coefficient, may be provided.

To maximize the repeater life span, it is essential that as much air aspossiblebe excluded from tank member 10. For this purpose, it isdesirable that every portion of tank member 10 not filled with apparatusor filler material be filled with oil. Any appreciable amount of airwithin tank member 10 will, because of the compressibility of air,greatly increase the required capacity of the pressure equalizingapparatus. Any oil having suitable insulating qualities could beemployed for fillingtank member 10. However, capacitor-type mineral oilis preferred for this purpose because of its excellent electricalqualities and because seepage of this type of oil into the interior ofcapacitive elements will produce a minimum change in the electricalcharacteristics thereof.

Moisture Within tank member 10 will tend to shorten the life ofelectronic components. For this reason, all components should bethoroughly dried. Apertures A and A in cover plate 14 are provided forevacuating and filling tank member 10. In service, these apertures areclosed with suitable plugs.

When the repeater is lowered to its operating position it will besubjected to a temperature drop which may be aslarge as 40 F. or more.Since most oils, suitable for filling tank member 10 have a relativelylarge volumetric temperature coefiicient, 0.00035 per degree F. being atypical value, means must be provided to fill the space left empty asthe oil contracts. In addition, any portions of'the tank member notinitially filled should be filled when the repeater is subjected tohydrostatic pressure. This is accomplished by expansion of bellows 33due to increasing hydrostatic pressure. If the interior of bellows 33were filled with sea water, a thin-walled metallic bellows couldnotconveniently be used because of corrosion problems. However, it isdesirable to employ a thinwalled metallic bellows because of itssensitive response to changes in hydrostatic pressure. Providing thetandem arrangement of piston 32 and bellows 33 permits the use of athin-walled metallic bellows. The reservoir of oil contained in thelower portion of cylinder 30 and in bellows 33 should be sufficientlylarge to permit bellows 33 to expand sufliciently to compensate for alldecreases in volume of oil within tank member 10.

It has been found impractical to construct a piston and cylinder.assembly which will completely prevent sea water from getting past thepiston. Furthermore, a substantially water-tight fit of piston andcylinder would tend to be relatively insensitive'to small changes inhydrostatic pressure. In the arrangement illustrated in Fig. 4, a smallamount of sea water seepage past piston 32 will not produce harmfulresults because the sea water will still be excluded from the portion oftank member 10 containing electronic apparatus. It is evident, however,that cylinder 30, piston 32 and bellows 33 should be constructed ofcorrosion resistant metal since each will be subjected to the corrosiveeffects or salt water.

Fig. 5, which is a section taken along line 55 of Fig. 4, shows the planarrangement of tank 10, glands 24, 24' and 25, cylinder 30 and bellows33.

For reasons set forth hereinbefore, it is desirable that thin-walledbellows 33 be not subjected directly to sea water. In the arrangementillustrated in Figs. 4 and 5, suitable separation is obtained by usingthe tandem arrangement of piston 32 and bellows 33. An importantadvantage of the tandem arrangement is that failure of either the pistonor bellows will not disable the repeater. More particularly, excessiveseepage of water past piston 32 will not admit sea water to theelectronic apparatus in tank 10. Similarly, a leak in bellows 33 willnot allow the oil from tank'10 to escape to the sea.

An alternative arrangement and one which provides a larger oil reservoirfor compensating voids in tank member is illustrated in Figs. 6 and 7.Elements in Figs. 6 and 7 corresponding to elements in Figs. 1 through 5are given like reference characters.

Referring now to Fig. 6, bellows member 33 is supported by nipple 36screwed into an aperture in cover plate-14. A second bellows member 40is mounted on cover plate 14. The walls of bellows member 40 should beformed of a material resistant to both oil and sea water. One suitablematerial is synthetic rubber. Cover plate 14 serves as the bottom memberof bellows 40, the synthetic rubber walls being fastened thereto withbolts. A metal plate 41, also fastened to the walls of bellows 40 withbolts, serves as the top of bellows 40. Since bellows 40 is mountedoutside tank member 10, bellows 40 will be subjected directly tohydrostatic pressure. Since both bellows 33 and 40 are filled with oiland since they are joined by nipple 36, pressure exerted on bellows 40will be transmitted to bellows 33 which, in turn, will transmit thepressure to the oil within tank 10.

t For mechanical protection of bellows 40, a metal plate 42 is disposedabove plate 41 and supported by four metal straps 43, 44, 45 and 46, ofwhich .only straps 43 and 44 are visible in Fig. 6, all four being shownin Fig. 7.

.In. Fig. 6 the connections of the cable conductors of cable 23 toglands 24 and 24' and the connections of the cable conductor of cable 22to gland 25 have been omitted for clarity. It is evident that cableentrance chamber 11 of Fig. 6 must be larger than cable entrance chamber11 of Fig. 1 because of the inclusion of bellows 40 in cable entrance 11of Fig. 6.

Fig. 7 is a section of Fig. 6 taken along line 7-7 and shows a plan viewof the cable entrance and bellows 40.

As in the case of the tandem piston-bellows arrangement of Figs. 4 and5, failure of either bellows 33 or bellows 40 of Figs. 6 and 7 will notresult in admission of sea water to the electronic apparatus of tank 10.An additional advantage of the double bellows arrangement is, thatvirtually no sea water will be admitted to bellows 33 :-b.ecause thesynthetic rubber walls of bellows 40 act as an effective gasket.

gThe procedures pointed out, together with the construction referred toin the foregoing are adequate to provide a satisfactory range ofpressure equalizing capacity in reasonable depths of water and underreasonable changes of temperature, a typical situation being 750 poundsper square inch hydrostatic pressure and a typical temperature being 40F.

. Referring to Fig. 8, it is seen that by the use of a vacuum pump 51, areduced pressure can be attained in chamber 57, when the valve 54 isopen, the valve 56 closed, and the valve 61 closed. Indicator 52consisting of a closed transparent vessel containing fluid and an inletdip tube, provides a convenient means of observing the progress ofevacuation from the size and frequency of. the bubbles which appeartherein. When a vacuum in the neighborhood of inches of mercury, asshown on gauge 71, has been obtained, regulating valve 63 is opened tointroduce dry nitrogen from the flask 62 into the chamber 57. Thisprocess, when repeated several times,.is effective in removing air,moisture and moisture vapor from the equipment enclosed in thecontainer. Immediately after the last introduction of nitrogen, pipe 84is removed, and the opening left in chamber 57 is plugged. Whensufficiently dehydrated, chamber 57 may be connected to container 64 ofoil 66 by opening valve 61. Application of vacuum from pump 51 will thencause chamber 57 to fill with oil. It is advantageous to arrest thisprocess at intervals by closing valve 61 and allowing pump 51 to run, sothat air confined or trapped in the interstices in the equipmentcontained in chamber 57 may be expanded and removed while near thesurface of the oil without being subjected to hydrostatic pressure froman excessive head of contained insulating oil standing above it in thechamber 57, which would limit the effectiveness of the pump 51 inremoving it. When chamber 57 is filled, valve 54 is closed, valve 61 isclosed, pipe 81 removed, and the opening thus left in chamber 57 isplugged. Valves 56 and 61 are then opened, valve 86 closed, and pump 51is operated, a vacuum being thereby applied to the space enclosedbetween the bellows 58 and 59, causing bellows 59 to contract, anddrawing further oil 66 from container 64 into chamber 57. Pipe 33connected to chamber 57 may then be re: moved and the opening plugged,after which the vacuum previously applied between diaphragms 58 and 59may be released and the pipe 82 connected thereto removed. Theinter-bellows chamber is now filled by pouring oil into it through theopening in the top plate of diaphragm 58 left by the removal of pipe 82,while the upper bellows is distended by a lifting force applied to thetop plate, and that opening is then plugged. By this technique air andmoisture are removed from the chamber, and the bellows 58 and 59 aresufficiently flexed in an outward direction to provide increasedvolumetric ca-' pacity in order to accommodate later contraction due tothe pressure of great depths of sea water acting on the contents of thechamber.

Fig. 9 illustrates another method of filling chamber 57; wherein apressure pump 67 is used to remove insulating oil 66 from the container64 and apply it under a pres sure indicated by gauge 63 through thecheck valve 68 into chamber 57. Dry nitrogen gas from flask 62 is firstapplied through regulating valve 63 to the chamber.

57 prior to filling the same with oil, and is exhausted therefrom byvacuum pump 91 having valve 93 open and valves 94 and 69 closed, after aslight pressure has been developed in chamber 57, the process beingrepeated slowly several times. This accomplishes drying of the interiorof chamber 57 and removal of air therefrom, as previously explained.When the dehydration and deaeration are completed, pipe 84 isdisconnected and the opening thereby left in chamber 57 is plugged. Withvalve 69 open, and acting as a vent, oil is forced, by pump 67 intochamber 57 until it is partly filled. With valve 94 closed, valve 69closed and valve 93 open, vacuum pump 91 is operated to remove entrappedgases. The last two steps are repeated until chamber 57 is filled. Pipe92 and valve 69 are then removed and the openings in chamber 57 plugged.Additional oil is supplied by pump 67 until diaphragm 59 is sufficientlycompressed. Pump 67 may then be stopped, the piping between it andchamber 57 removed, and the opening therein plugged, while check valve68 prevents leakage of oil during that process, and also during anytemporary interruptions which may occur in the pumping due to break-'age or failure of equipment. The chamber between diaphragms 58 and 59 isthen poured full of oil through opening 82' while diaphragm 58 isdistended mechanically, and opening 82' is then plugged.

In Fig. 10 is shown an arrangement for filling chamber 57 withinsulating oil 66 from container 64, which presents advantagessuificient to render it the method of choice. Vacuum pump 51 isconnected to chamber 57 through indicator 52, valve 54 and pipe 74 withgauge 71 attached thereto, all previously described. After removal ofair, moisture, and moisture vapor from chamber 57, with the aid ofnitrogen flask 62, and regulator valve 63, as described for Fig. 8, thepipe 84 is removed, and the opening left thereby in chamber 57 isplugged. The valve 61 is then opened to permit an inflow of oil 66 fromcontainer 64 to chamber 57 as vacuum pump 51 is operated with valve 54open. Check valve 72 is located at the foot of dip tube 73 in the pathof this oil, and closes to prevent its escape from the tank 57. At thecompletionof pumping and filling and the removal of entrapped air, aspreviously described for Fig. 8, valve 54 is closed, pipe 74 removed andthe opening left thereby in chamber 57 plugged. Valve 56 is then openedand the pump 51 operated to collapse bellows 59, valve 61 remainingopen, thereby withdrawing an additional quantity of oil 66 fromcontainer 64 into chamber 57. Pipes 76 and 83 are then disconnected andthe opening in chamber 57 left by the removal of pipe 83 is plugged. Theinter-bellows chamber 77 is poured full of oil through the opening fromwhich pipe 76 was removed, while bellows 58 is distended by an upwardlyapplied force to its upper surface. The opening in bellows 58 is thenplugged.

It is seen that both bellows 58 and 59 are left in an upwardly flexedcondition, providing them with substantially full travel available forthe compensation of compressive volume changes due to pressure of seawater at great depths. Moreover, the provision of check valve 72 in theoil dip tube '73 prevents any outflow of oil from occurring due to anaccidental or temporary interruption in the operation of vacuum pump 51.In addition, when valve 61 and its associated piping 33 is disconnectedpreparatory to plugging the opening therefor in chamber 57, the level ofoil at that opening is not dependent upon the degree of pressure in tank57, but is fixed and stable such that a plug readily can be inserted inthe opening without danger of loss of oil from or of entrance of airinto tank 57. Since the use of vacuum pump 51 is desirable in order toremove entrapped air from the chamber 57 in any event, the furtheradvantages of the arrangement of Fig. already mentioned are attainedWithout the use of additional pumping equipment.

In Figs. 8 to 10 we have shown means associated with the container bywhich voids internal to chamber 57 are substantially reduced oreliminated and the deleterious effects thereof obviated when the chamberis subjected to conditions of high hydrostatic pressure such as occur atdepths from 600 fathoms to over 1000 fathoms. It has been found to beadvantageous to operate submarine cable repeaters at such greater depthsin order to amplify the incoming signals before they encounterinterference produced by another cable which the operating cable mayparallel or cross, for the purpose of reducing cross-talk or mutualinterference between the signal currents traveling within the cables.Hydrostatic pressures from approximately 1800 pounds to over 3000 poundsper square inch are encountered in such cases and are successfullyaccommodated hereby.

While the invention has been described in particular embodiments thereofand in particular uses, it is not desired that it be limited thereto forobvious modifications thereof will occur to those skilled in the artwithout departing from the spirit and the scope of the invention as setforth in the appended claims.

What is claimed is:

1. In a submersible device comprising apparatus enclosed in a casingfilled with an insulating liquid for operation in an ocean or other bodyof deep water, and in which an extensible structure is mounted in a wallof the casing for changing the volumetric capacity of the casing inaccordance with the hydrostatic pressure encountered; the method ofincreasing the maximum pressure which said extensible structure willexert on the liquid within the casing to increase the range of depths ofwater in which the apparatus 'can operate comprising the steps ofalternately evacuating said casing to a pressure less than atmosphericpressure and filling the evacuated casing with an anhydrous inert gasthroughout at least one cycle of such alternations, there' afteralternately inserting into the said casing an insulating liquid in theamount of a fractional part of the volumetric capacity of the saidcasing and evacuating the space above the liquid in said casingthroughout a pm: rality of such alternations until the casing isfillcdwith the said insulating liquid, causing the said extensiblestructure to deform in a direction to enlarge the volumetric capacity ofsaid casing, further filling said-casing to an increased maximumcapacity thereof with said liquid, and sealing the casing.

r 2. In a submersible device comprising apparatus enclosed in a casingfilled with an insulating liquidv for operation in an ocean or otherbody of deeptwater, and in which a bellows structure is mounted in awall of the casing and located entirely within the casing, a sec-: ondbellows structure similarly mounted is located withf out the casing andcommunicates with the first said bellows structure toform a cavitycommon thereto, and a liquid fills said cavity for transmitting pressureto the insulating liquid within thecasing in accordance with theexternal hydrostatic pressure encountered; the method of increasing themaximum pressure which said bellows structure will exert on the liquidwithinthe casing to increase the range of depths of water in which theap paratus can operate comprising the steps of alternately evacuatingsaid casing to a pressure less than atmospheric pressure and filling theevacuated casing with an anhydrous inert gas throughout at least onecycle of such alternations, thereafter alternately inserting 'into thesaid casing an insulating liquid in the amount of a fractional part ofthe volumetric capacity of the said casing and applying a vacuum to thespace above the liquid in said casing throughout a plurality ofsuchalternations until the casing is filled with the said insulating liquid,evacuating the said cavity to compress the first of said bellowsstructures and further filling thesaid casing with the said insulatingliquid, sealing the casing, distending the second bellows, filling thesaid cavity witha liquid while the said first bellows member remains inacompressed condition, and while the said second bellows member isdistended, and sealing the said cavity.

3. In a submersible device comprising apparatus errclosed in a casinghaving therein a filling pipe with a check valve closing outwardly,filled with an insulatin'g': liquid for operation in an ocean or otherbody of deep water, and in which a bellows structure is mounted in awall of the casing and located entirely within the cas= ing, a secondbellows structure similarly mounted is located without the casing, andcommunicates withthe first said bellows structure to form a cavitycommon thereto, and a liquid fills said cavity, for transmittingpressure to the insulating liquid within the casing in accordance withthe external hydrostatic pressure encountered; the method of increasingthe'maximum' pressure which said bellows structure will exert on theliquid within the casing to increase therange of depths of water inwhich the apparatus can operate comprising the steps of alternatelyfilling the said casing with an anhydrous inert gas and removing thesaid gas from the casing through at least one cycle of suchalternations, thereafter filling the said casing with an insulatingliquid, forcing a further amount of saidliquid into said casing underpressure thereby to compress said second bellows structure, and fillingthe said cavity with liquid under pressure thereby to distend the saidsecond bellows'stru'cture, and sealing said casing and said cavity.

4. In a submersible device comprising apparatus en,

closed in a casing having therein a filling pipe witha check valveclosing outwardly, filled with an insulating liquid for operation in anocean or other body of deep water, and in which a bellows structure ismountedin" a wall of the casing and located entirely within the cas ing,a second bellows structure similarly mounted is located without thecasing and communicates with the first said bellows structure to form acavity therebetween, and a liquid fills said cavity for transmittingpressure to the insulating liquid within the casing in accordance withthe hydrostatic pressure encountered; the method of increasing themaximum pressure which said bellows structure will exert on the liquidWithin the casing to increase the range of depths of Water in which theapparatus can operate comprising the steps of alternately evacuatingsaid casing to a pressure less than atmospheric pressure and filling theevacuated casing with an anhydrous inert gas throughout at least onecycle of such alternations, thereafter alternately inserting into thesaid casing an insulating liquid in the amount of a fractional part ofthe volumetric capacity of the said casing and evacuating the spaceabove the liquid in said casing throughout a plurality of suchalternations until the casing is filled with the said insulating liquid,evacuating the said cavity to compress the first said bellows structureand further filling the said casing with the said insulating liquid,sealing the casing, distending the second bellows member, filling thesaid cavity With a liquid While the said first bellows member remains ina compressed condition and While the said second bellows member isdistended, and sealing the said cavity.

No references cited.

